PrerenderingLoader initial integration with PrerenderManager/PrerenderHandle

chrome/browser/android/offline_pages/prerendering_loader.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/android/offline_pages/prerendering_loader.h"
 
+#include "base/location.h"
+#include "base/logging.h"
+#include "base/threading/thread_task_runner_handle.h"
+#include "chrome/browser/profiles/profile.h"
 #include "content/public/browser/browser_context.h"
+#include "content/public/browser/browser_thread.h"
 #include "content/public/browser/web_contents.h"
 #include "ui/gfx/geometry/size.h"
 
 namespace offline_pages {
 
-PrerenderingLoader::PrerenderingLoader(
-    content::BrowserContext* browser_context) {}
+PrerenderingLoader::PrerenderingLoader(content::BrowserContext* browser_context)
+    : state_(State::IDLE), browser_context_(browser_context) {
+  adapter_.reset(new PrerenderAdapter(this));
+}
 
-PrerenderingLoader::~PrerenderingLoader() {}
+PrerenderingLoader::~PrerenderingLoader() {
+  CancelPrerender();
+}
 
-bool PrerenderingLoader::LoadPage(
-    const GURL& url,
-    const LoadPageCallback& callback) {
-  // TODO(dougarnett): implement.
-  return false;
+bool PrerenderingLoader::LoadPage(const GURL& url,
+                                  const LoadPageCallback& callback) {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+  if (!IsIdle()) {
+    DVLOG(1)
+        << "WARNING: Existing request in progress or waiting for StopLoading()";
+    return false;
+  }
+  if (!CanPrerender())
+    return false;
+
+  // Create a WebContents instance to define and hold a SessionStorageNamespace
+  // for this load request.
+  DCHECK(!session_contents_.get());
+  session_contents_.reset(content::WebContents::Create(
+      content::WebContents::CreateParams(browser_context_)));
+  content::SessionStorageNamespace* sessionStorageNamespace =
+      session_contents_->GetController().GetDefaultSessionStorageNamespace();
+  gfx::Size renderWindowSize = session_contents_->GetContainerBounds().size();
+  bool accepted = adapter_->StartPrerender(
+      browser_context_, url, sessionStorageNamespace, renderWindowSize);
+  if (!accepted)
+    return false;
+
+  DCHECK(adapter_->IsActive());
+  callback_ = callback;
+  state_ = State::PENDING;
+  return true;
 }
 
 void PrerenderingLoader::StopLoading() {
-  // TODO(dougarnett): implement.
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+  CancelPrerender();
+}
+
+bool PrerenderingLoader::CanPrerender() {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+  return adapter_->CanPrerender();
+}
+
+bool PrerenderingLoader::IsIdle() {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+  return state_ == State::IDLE;
+}
+
+bool PrerenderingLoader::IsLoaded() {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+  return state_ == State::LOADED;
+}
+
+void PrerenderingLoader::SetAdapterForTesting(
+    std::unique_ptr<PrerenderAdapter> prerender_adapter) {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+  adapter_ = std::move(prerender_adapter);
+}
+
+void PrerenderingLoader::OnPrerenderStart() {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+  DCHECK(state_ == State::PENDING);
+  state_ = State::LOADING;
+}
+
+void PrerenderingLoader::OnPrerenderStopLoading() {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+  // TODO(dougarnett): Implement/integrate to delay policy here.
+  HandleLoadEvent();
+}
+
+void PrerenderingLoader::OnPrerenderDomContentLoaded() {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+  // TODO(dougarnett): Implement/integrate to delay policy here.
+  HandleLoadEvent();
+}
+
+void PrerenderingLoader::OnPrerenderStop() {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+  HandleLoadingStopped();
+}
+
+void PrerenderingLoader::HandleLoadEvent() {
+  // If still loading, check if the load succeeded or not, then update
+  // the internal state (LOADED for success or IDLE for failure) and post
+  // callback.
+  // Note: it is possible to receive a load event (e.g., if timeout-based)
+  // after the request has completed via another path (e.g., canceled) so
+  // the Loader may be idle at this point.
+  if (!IsLoaded() && !IsIdle()) {

[pasko, 2016/05/23 20:05:41]

Less nesting an less negation seems more readable:

if (IsLoaded() || IsIdle())
  return;

content::WebContents* contents = ...

[dougarnett, 2016/05/23 21:43:54]

Done.

+    content::WebContents* contents = adapter_->GetWebContents();
+    if (contents) {
+      state_ = State::LOADED;
+      base::ThreadTaskRunnerHandle::Get()->PostTask(
+          FROM_HERE,
+          base::Bind(callback_, Offliner::RequestStatus::LOADED, contents));
+    } else {
+      // No WebContents means that the load failed (and it stopped).
+      HandleLoadingStopped();
+    }
+  }
+}
+
+void PrerenderingLoader::HandleLoadingStopped() {
+  // Loading has stopped so unless the Loader has already transistioned to the
+  // idle state, clean up the previous request state, transition to the idle
+  // state, and post callback.
+  // Note: it is possible to receive some asynchronous stopped indication after
+  // the request has completed/stopped via another path so the Loader may be
+  // idle at this point.
+  if (!IsIdle()) {
+    if (adapter_->IsActive()) {
+      DVLOG(1) << "Load failed: " << adapter_->GetFinalStatus();
+      adapter_->DestroyActive();
+    }
+    // Request status depends on whether we are still loading (failed) or
+    // did load and then loading was stopped (cancel - from prerender stack).
+    Offliner::RequestStatus request_status =
+        IsLoaded() ? Offliner::RequestStatus::CANCELED
+                   : Offliner::RequestStatus::FAILED;
+    // TODO(dougarnett): For failure, determine from final status if retry-able
+    // and report different failure statuses if retry-able or not.
+    session_contents_.reset(nullptr);
+    state_ = State::IDLE;
+    base::ThreadTaskRunnerHandle::Get()->PostTask(
+        FROM_HERE, base::Bind(callback_, request_status, nullptr));
+  }
+}
+
+void PrerenderingLoader::CancelPrerender() {
+  if (adapter_->IsActive()) {
+    adapter_->DestroyActive();
+  }
+  session_contents_.reset(nullptr);
+  if (!IsLoaded() && !IsIdle()) {
+    base::ThreadTaskRunnerHandle::Get()->PostTask(
+        FROM_HERE,
+        base::Bind(callback_, Offliner::RequestStatus::CANCELED, nullptr));
+  }
+  state_ = State::IDLE;
 }
 
 }  // namespace offline_pages